You should not "test" at all bc CO is already lethal in low doses. The amount of CO in that cylinder should be much more than enough to kill u if you open it in a tent or small room for example. Keep in mind that this can be dangerous for others. Don't use it in an apartment building for example.
Info about how to use a CO cylinder:
Practical instruction on how to kill yourself using the inhalation of carbon monoxide gas
www.jerryhunt.org